1. Grease and line a loaf tin with grease proof paper, leaving paper hanging over the sides of the tin (this will help you lift the slice out later).
2. Place the dates, peanut butter, vanilla and roasted peanuts in a food processor and process until this mixture is thick and combined. This may take a couple of minutes and need scraping and stirring.
3. Turn the date mixture into a large bowl and pour over the rice bubbles. Mix well with a spatula until combined. Transfer to the prepared tin and press down into an even layer. Set aside in the fridge for 30 minutes to chill.
4. Take the slice from the fridge and evenly pour over the melted chocolate, spreading with the back of a spoon. Refrigerate again until chocolate is set and then holding the paper on with side lift from the tin. Using a sharp knife, cut the slice into bars.